In general, a cartridge or blade unit of a safety razor has at least one blade with a cutting edge which is moved across the surface of the skin being shaved by means of a handle to which the cartridge is attached. The cartridge may be mounted detachably on the handle to enable the cartridge to be replaced by a fresh cartridge when the blade sharpness has diminished to an unsatisfactory level, or it may be attached permanently to the handle with the intention that the entire razor be discarded when the blade or blades have become dulled. Razor cartridges usually include a guard which contacts the skin in front of the blade(s) and a cap for contacting the skin behind the blade(s) during shaving. The cap and guard may aid in establishing the so-called “shaving geometry”, i.e., the parameters which determine the blade orientation and position relative to the skin during shaving, which in turn have a strong influence on the shaving performance and efficacy of the razor. The guard may be generally rigid, for example formed integrally with a frame or platform structure which provides a support for the blades.
Guards are present on many shaving razors and are intended to stretch the skin; however, these guards also have a propensity to press hair against the skin. The interaction of these guards with hair is analogous to rolling a weighted drum over grass just prior to cutting the grass with the blade of a lawn mower. The grass, similar to hair on the skin, cannot be cut effectively and efficiently if it is not oriented generally perpendicular to the blade.
Standard shaving razor guards are able to cut short hairs rather effectively because short hairs are generally stiff and oriented generally perpendicular to the blade. Hair growth may vary depending on the individual, as well as the area of the body being shaved. Typically short hairs are characterized as growth of approximately twenty-four hours. As hair grows longer it has a tendency to bend over and lay flat against the surface of the skin in an orientation that is more parallel to the surface of the skin. Standard shaving razors are less effective for cutting longer hairs because the blade (or blades) has a tendency to skive or cut the hair at an angle. The blade does not consistently cut the longer hairs close to the skin surface because of the general parallel orientation of the hair. Some hairs may lay flat such that the blade of the razor passes over the hairs without cutting them. The user often has to shave the same area repeatedly to cut hairs that were either uncut or not cut close enough to the skin surface, resulting in increased skin irritation.